Insects are a class of invertebrates that have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. The number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing animal life forms on Earth. Adult insects typically move about by walking, flying, or sometimes swimming. Some species, such as water striders, are capable of walking on the surface of water. Social insects, such as termites, ants and many bees and wasps, live together in large well-organized colonies.